A Piezo-Optical Effect in Lead Nitrate

A piezo-optical effect has been discovered in Lead nitrate crystals. A possible mechanism of the piezo-optical effect in divalent nitrates is discussed. It’s assumed that the cause of the piezo-optical effect in the crystals is the displacement of the Nitrogen atoms relatively to the planes of Oxygen atoms in NO3– groups under application of mechanical stress. Due to this shift, the planar NO3– groups become pyramidal, with the Nitrogen atoms at the apexes of the pyramids. It is noted that it’s precisely such a displacement that can cause a deformation of the optical indicatrix. In the absence of mechanical stress, the optical indicatrix has the shape of a sphere, since light birefringence is not observed in this case. Under mechanical stress the optical indicatrix becomes an ellipsoid. To observe the piezo-optical effect, single crystals of Lead nitrate of equilibrium shape, which is cuboctahedron, were used. These single crystals were grown from a saturated seed solution of Pb(NO3)2 by a slow temperature decreasing method. The paper describes a setup for piezo-optical coefficients of Lead nitrate measurements, which was specially created for research. It is noted that for crystals of the Th group the following components of the matrix of piezo-optical coefficients are independent: 11, 12, 13, 44. It where these components or their combinations that we measured. The measurements have shown that the piezo-optical optical coefficients of Lead nitrate have rather large values, so the crystals can be used as a material for piezo-optical transducers.